1. Field of the Invention
This invention relates to a brakable wheel hub device, more particularly to a brakable wheel hub device adapted to detachably secure a brake disk so as to be rotatably mounted on a wheel axle of a bicycle.
2. Description of the Related Art
A conventional bicycle wheel hub, such as that disclosed in U.S. Pat. No. 6,371,252 B1 and U.S. Pat. No. 6,571,920 B1, is coupled to a brake disk to be rotatably mounted on a wheel axle of a bicycle, and generally includes a hub shell rotatably coupled to a hub axle, and having external peripheral splines, and a positioning adapter having internal surrounding splines to engage the external peripheral splines, and a connecting surface for fixing the brake disk. Due to the particular construction of the hub shell, manufacturing cost; is relatively high. To improve this problem, in U.S. patent application Ser. No. 10/392,992 which is now U.S. Pat. No. 6,854,569 B2, as shown in FIG. 1, the applicant disclosed a brakable wheel hub device 10 that comprises a wheel hub shell 13, a positioning ring 14, and a surrounding locking member 15.
The wheel hub shell 13 has a surrounding shell wall 131 which is rotatably mounted on a wheel axle 11 of a bicycle along an axis 110 by means of bearing members 12, and which has an internally threaded section 136 extending in an axial direction, and a disk securing portion 134 which extends from the surrounding shell wall 131 radially and outwardly, and which has a plurality of axially extending insert holes 135 (e.g., six insert holes). Further, two spoke mounting flanges 132, 133 extend radially and outwardly from the wheel hub shell 13 for engaging wheel spokes (not shown). A brake disk 20 is a standard brake disk, and has six angularly displaced through holes 21. The brake disk 20 surrounds the axle 11, and is disposed to align the through holes 21 with the insert holes 135, respectively.
The positioning ring 14 surrounds the axle 11, and includes inside and outside surrounding surfaces 141, 145 proximate to and distal from the brake disk 20, respectively. A plurality of protrusions 142 (e.g., six protrusions) extend from the inside surrounding surface 141 in the axial direction, and are angularly displaced from one another about the axis 110. Each protrusion 142 includes a larger-diameter segment 143 which extends from the inside surrounding surface 141 and which can be mounted in the respective through hole 21 in the brake disk 20, and a smaller-diameter segment 144 which extends from the larger-diameter segment 143 and which can be fitted into the respective insert hole 135 in the disk securing portion 134.
The surrounding locking member 15 includes an insert segment 152 which has an externally threaded section to threadedly engage the internally threaded section 136, and an abutting segment 151 which extends radially from the insert segment 152.
After the protrusions 142 are brought to pass through the respective through holes 21 and to be fitted into the respective insert holes 135 so as to place the brake disk 20 in a spline engagement with the wheel hub shell 13, the surrounding locking member 15 is mounted such that the externally threaded section threadedly engages the internally threaded section 136, and such that the abutting segment 151 frictionally abuts against the outside surrounding surface 145 of the positioning ring 14, thereby securing the brake disk 20 to the wheel hub shell 13.
To disassemble the brake disk 20 from the axle 11, the surrounding locking member 15 is operated to be screwed out of the wheel hub shell 13 so that the positioning ring 14 and the brake disk 20 can be easily detached from the axle 11.
With the construction as such, the wheel hub shell 13 of the brakable wheel hub device is easier to manufacture, and assembly and disassembly of the brake disk 20 to and from the wheel hub shell 13 are convenient to conduct.
It is desirable to improve the aforesaid brakable wheel hub device to provide an enhanced stabilizing force to the brake disk 20 during a braking action so as to reduce an impact resulting from a shearing force between the protrusions 142 and the through holes 21 and the insert holes 135.